Arcless interrupter



March 14, 1967 l.. J. GOLDBERG 4 Sheets-Sheet l fn Ver; or.' L e on CZ Go/c/,e/jg,

l.. J. GOLDBERG ARCLESS INTERRUPTER March 14, 1967 O1^igna1 Filed Aug. 5, 1963 eg. by f@ /3 A Cor/72g.

March 14, 1957 L.. J. GOLDBERG 3,309,570

l ARCLESS INTERRUPTER Original Filed Aug. 5, 1965 4 Sheets-Sheet 5 /3/ anni A cof/mmm caf/005mm March 14, 1967 L. J. GOLDBERG 3,309,570

ARCLESS INTERRUPTER original Filed Aug. 5, 1965 4 sheetsssneet f1 y by Mw/gg@ H/Ls A t orwey.

UnitedStates Patent O 3,309,570 ARCLESS INTERRUPTER Leon J. Goldberg, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York Continuation of application Ser. No. 299,913, Aug. 5, 1963. This application May 16, 1966, Ser. No. 559,670 21 Claims. (Cl. 317-11) This invention relates to an arcless interrupter and is a continuation of my application Ser. No, 299,913, filed August 5, 1963, now abandoned.

More specifically, the invention relates to an arcless interrupter for interrupting either direct current or alternating current supplied to an electrical load by means of a set of separable contacts without producing a substantial electric arc between the contacts during the interruption process.

In many electric circuits used today, it is often necessary to switch large currents in the order of hundreds and even thousands of amperes or greater. To do this, circuit interrupters are employed which comprise a set of physically separable contacts which upon separation, interrupt the electric current liow through the device. While interrupting large currents of this order of magnitude, an electric arc discharge normally is established between the two separable contacts as they separate. This arc lasts for a iinite period, and requires special structures to be extinguished. Many different structures have been employed for both elongating the arc, and driving it into an arc chute which absorbs energy from the arc. Some of the more commonly used devices of this nature employ a magnetic eld transverse to the arc or air blasts either axially aligned with or transverse to the arc, as well as oil baths. In the case of the magnetic blowout interrupter, a magnetic field is formed by a series coil and core transverse to the arc, and accomplishes arc extinction by driving the arc into an associated arc chute structure. These structures are large for large current ratings, and difficult to manufacture. Additionally, they allow the arc to continue for predetermined periods thereby introducing undesired switching transients into the power system, and further require replaceable contacts whose operating life is greatly shortened the longer an arc is allowed to continue. To overcome these problems, and to obviate the need for such devices and structures, the present invention was devised.

It is therefore a primary object of the invention to provide a new and improved arcless interrupter for interrupting either direct current or alternating current supplied to an electric load by means of a set of separable contacts without producing any substantial electric arc between the contacts during the interruption operation.

In practicing the invention, an arcless circuit interrupter is provided which comprises a set of physically separable contacts connected in circuit relationship with a load for interrupting current to the load. A commutating capacitor, and a fast acting gate controlled conducting device (preferably a silicon controlled rectifier) are connected in a closed series circuit loop with the separable contacts so that the gate controlled conducting device serves to connect the capacitor across the contacts upon being rendered conductive. Electronic sensing and control means are operatively coupled to the contacts and to the control gate of the fast acting gate controlled conducting device for sensing the increase in potential across the contacts as they start to open, and thereby turn on the fast acting gate controlled device in response to the opening of the contacts. The circuit is completed by means for charging the commutating capacitor to an energy level and polarity such as to prevent the formation yof any substantial arc or gaseous discharge across the contacts upon the -discharge of the capacitor when the contacts YCC start to open. In operation, the arcless interrupter serves to divert the current from the physically separable contacts immediately after they separate, and to impose across the contacts at the same time a reverse voltage that aids in quickly de-ionizing the space between the contacts. This is achieved by means of the commutati'ng capacitor which is precharged to the proper voltage and polarity, and suitably switched in to the circuit by the fast acting gate controlled conducting device.

Other objects, features and many of the attendant advantages of this invention will be appreciated more readily as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein like parts in each of the several gures are identified by the same reference character, and wherein:

FIGURE l is a functional `block diagram of an arcless circuit interrupter constructed in accordance with the invention; Y

FIGURE 2 is a series of schematic representations of a number of gate controlled conducting devices suitable for use in the arcless circuit interrupter illustrated in func tional block diagram form in FIGURE l;

FIGURE 3 is a schematic circuit diagram of one specific form of a satisfactory circuit interrupter constructed in accordance with the invention;

FIGURE 4 is a schematic circuit diagram of still another form of circuit interrupter constructed in accordance with the invention which makes possible substantially instantaneous arcless interruption immediately after closing of the circuit on a load;

FIGURE 5 is a schematic circuit diagram of an arcless interrupter constructed in accordance with the invention which provides over-current protection;

FIGURE 6 is a schematic circuit diagram of still another specific form of arcless circuit interrupter suitable for use with high voltage circuits wherein the high voltage current carrying switching circuit components are separated from the low voltage sensing circuit cornponents;

FIGURE 7 is a schematic circuit diagram of an alternating current arcless circuit interrupter constructed in accordance with the invention;

FIGURE 8 is a functional block diagram of a form of arcless circuit interrupter which employs the distributed capacitance of a supply cable as a part thereof;

FIGURE 9 is a schematic circuit diagram of a cornplete arcless interrupter employing the distributed capacitance of a supply cable as a part of the interrupter; and

FIGURE l0 is a schematic circuit diagram of a complete high voltage direct current circuit interrupter employing the principles of the present invention.

The arcless circuit interrupter shown in FIGURE 1 of the drawings comprises a set of physically separable contacts indicated at 11 which are connected in series circuit relationship with a load 12 across a source of direct current indicated by the terminals marked plus and minus The set of physically separable contacts 11 comprises a part of a solenoid actuated switch havin-g a control winding indi-cated at 13 which may be connected in series circuit relationship with an on-otf knife switch 14 across the direct current supply. A commutating capacitor 15 is provided which has one of its plates or electrodes operatively connected to the junction of the load 12 and one of the contacts of the set of movable contacts 11. It should be noted that while in the illustration and following description a single capacitor having a single set of plates is disclosed, the capacitor is intended to depict any sort of capacitance which may be comprised by a capacitance bank made up from a plurality of condensers, for example, or from some other similar arrangement such as those which will be described in connection with FIGURES 8 and 9 later. Also, it should be noted, that while the set of physically separable contacts 11 is illustrated as a switch having a single set of contacts, the principles of the invention w-ill operate equally well with switches having multiple contacts, or with multiple sets of switches; but for the sake of simplicity only a single set of contactors is illustrated. A fact acting gate controlled conducting means 16 is operatively connected between the remaining plate of the commutating capacitor 15 and the remaining contact of the set of physically separable contacts 11, and upon being rendered conductive serves to couple the capacitor 15 across the set of separable contacts 11. The fast act-ing gate controlled conducting means 16 may comprise any fast responding electronic device such as those illustrated schematically in FIGURES 2(a) through 2(d). However, in preferred arrangements of the interrupter, the gate controlled conducting means 16 comprises a silicon controlled rectifier because of its high sensitivity and speed of response. For higher voltage ratings, it may be desirable to employ a series arrangement of silicon controlled rectifier and a two-electrode gap such as shown in FIGURE 2(d). For other applications, thyratron, ignitron or similar Igas discharge devices such as shown in FIGURE 2(b) may be used, or a three-electrode gap such as shown in FIGURE 2(0) may be preferred.

The fast actin-g gate controlled conducting means 16 has its control gate operatively connected to a non-mechanical, electronic sensing and ycontrol circuit means 17 which in turn is operatively connected to one of the separable contacts 11. By this arrangement the circuit means 17 will sense the increase in potential occurring across the set of contacts 11 as they start to separate. The arcless circuit internupter is completed by a charging circuit means 18 which serves to charge the commutating capacitor 15 to a polarity and sucient voltage level so that upon its discharge when the fast acting gate controlled conducting means 16 is rendered conductive, the capacitor discharge current circulated in the closed series loop comprised by the separable contacts, the commutating capacitor and the gate controlled conducting means, is sucient to reduce the load current ow through the contacts to zero or perhaps even to cause a reverse current to flow through the contacts with respect to the initial load current to thereby prevent the formation of any substantial arc across the contacts. By connecting the charging circuit 18 and the commutating capacitor 15 in the above-described manner, it is `assured that the polarity of the potentials `across the capacitor 15 will be such as to divert the current through the circuit away Vfrom contacts 11 as they start to separate, and to cause the polarity of the potential across the contacts to be reversed so as to prevent the formation of any substantial arc across the contacts as they start to open, and to yde-ionize the space between the contacts.

In operation, it is assumed that the contacts 11 are closed so that current is being supplied to load 12. If it is desired to interrupt the current at the load 12, the switch 14 is opened thereby de-energizing the control winding 13 which releases the contacts 11 and allows them to start to open. As the contacts 11 start to open, the increase in potential across the contacts will cause the sensing and control circuit 17 to fire the gate `controlled conducting means 16 which preferably comprises a silicon controlled rectifier. For example, as the contacts commence to open, .the voltage across the contacts rises from the voltage drop across the contacts which is in the neighborhood of a few millivolts rises toward the full line voltage. When this increase in potential reaches a magnitude in the order of a few volts, which occurs almost instantaneously, the gate controlled means is rendered conductive. Typically, the increase in -potential across the contacts may rise from a few millivolts to the neighborhood of 8 volts in one microsecond. Upon the gate controlledconducting -means 16 being rendered con! ductive, the charge on the commutating capacitor 15 is immediately coupled across the contacts 11. The capacitor 15 has been charged by the charging circuit 18 to a potential approximately equal to the potential of the D.C. supply source, and having the polarity indicated. It should be noted that the commutating capacitor may be charged to other values depending upon the value of the commutating capacitor 15, the value of la discharge current limiting resistor if one is used, and the load current to be commutated off, and may be any desired value with respect to t-he supply voltage provided it is adequate to accomplish the above effect. Upon the gate controlled conducting means 16 being rendered conductive, the path through the commutating capacitor 15 serves to dive-rt the current from the contacts 11 as they start to separate. In addition, the potential across the commutating capacitor 15 adds to the potential of the D.C. supply source to approximately double the potential across the load 12 (in the example cited). This results in dropping the potential at the point 19 to a value less than the negative potential of the D.C. supply source thereby reversing the potential across the contacts 11.` Reversal of the potential across the contacts 11 results in the prevention of the formation of any substantial arc across these contacts as they continue to separate, and deionization of the space between the contacts, and may even result in a small reverse current flow across the contacts. In this manner, arcless interruption of the current flow to the load 12 is achieved.

FIGURE 3 of the drawings is a schematic circuit diagram of one specific form of arcless circuit interrupter constructed in accordance with the invention. The arcless circuit interrupter in FIGURE 3 comprises a set of physically separable contacts 11 connected in series circuit relationship with a load resistor 21 across a source of direct current supply. The set of separable contacts 11 is actuated by a control winding or pick-up and holding coil 13 which in turn is energized through an on-oif switch 14 connected in series circuit relationship with the control winding 13 across the `direct current power supply. A commutating capacitor 15 has one of its plates connected to the junction of the load resistor 21 and the contacts 11, and its remaining plate connected to a silicon controlled rectifier 22 through a current limiting resistor 23. The control gate of the silicon controlled rectier 22 is connected to an electronic sensing and control circuit comprised by a current limiting resistor 24, blocking diode 25 and a fuse 26 connected in series circuit relationship between one of the contacts 11 and the control gate of the controlled rectifier 22. The circuit is completed by a resistor 27 connected between the positive terminal of the direct current power supply and commutating capacitor 15. By this arrangement, when the circuit is supplying load current to the load 21, the upper plate of the capacitor 15 will be at the potential of the negative bus, and the bottom plate of the capacitor 15 is charged to almost the positive bus voltage.

In opera-tion, upon the on-off switch 14 being opened, the control Winding 13 releases the contacts 11 to allow them to open and interrupt current flow through the load resistor 21. As a consequence, the voltage across -the contacts will rise from nearly zero value to about 15 or 2O volts before any arc will appear? across the contacts. This initial rise in voltage across the contacts lto some value less than an arc producing voltage (about 8 volts) is utilized to excite the gate of the silicon controlled rectier 22 through the sensing and control circuit comprised by resistor 24, blocking d-iode 25 and the fuse 26. Upon the silicon controlled rectifier 22 being rendered conductive, since the commutating capacitor 15 is charged with its upper plate at its negative bus voltage, almost double the system voltage will force current from the positive bus terminal through the load resistor 21, the capacitor 15, limi-ting resistor 23 and the silicon controlled rectifier 22 to the negative bus terminal. This produces a voltage;

drop across the load resistor 21 which is greater than the line voltage, and consequently the potential of the upper plate of the commutating capacitor 15 will drop below the potential of the negative bus terminal. This results in reversing the polarity of the voltage across the contacts 11 which now will be in opposition to the flow of normal load current through the contactor, and the space between the contacts will :be de-ionized so that the formation of any substantial arc discharge across the separated contacts is prevented. The value of the discharge current from capacitor 15 is determined primarily by the value of the potential to which it is charged, and the value of the current limiting resistor 23. This value is adjusted so that the load current through the contacts is reduced to zero, or nearly to zero, or may be even reversed with respect to the direction of the initial load current. Accordingly, it can be appreciated that by varying the value of the discharge current limiting resistor 23, the magnitude of the commutating capacitor discharge current can be controlled to provide a desired form of arcless interrupt-ion.

After the capacitor 15 is discharged, the full line voltage appears across the open contacts 11. Therefore the silicon controlled rectifier which temporarily remains in the conducting state must be protected. For this reason, the value of the charging resistor 27 is adjusted so that the current through the silicon controlled rectifier 22 after contacts 11 are open is maintained below the holding current of the SOR, and the silicon controlled rectifier will turn off upon the contacts 11 again being closed to remove the positive potential from the gate. v

In the particular circuit shown in FIGURE 3, a general purpose contactor General Electric Company type IC 2800-1617 was used having a rat-ing of 600 volts at 50 amps. A 250 volt direct current power supply was used with the load resistor 21 having a value of 5 ohms, the capacitor 15 having a value of 10 microfarads, limiting resistor 23 a value of 1.6 ohms, resistor 27 a value of 220 kilo-ohms, and the limiting resistor 24 having a value of 3.5 kilo-ohms.

FIGURE 4 is a schematic circuit diagram of still a different form of c-ircuit interrupter-constructed in accordance with the invention. The circuit of FIGURE 4 is quite similar to the circuit shown in FIGURE 3 of the drawings with the exception that an additional means is provided for add-ing a precharge to the commutating capacitor 15 in advance of closing the contacts 11 and supplying load cturent to the load device V12. By this means, in the event that a fault exists at the time ofclosing on the load, the commutating capacitor 15 will be precharged so that `arcless interruption can occur immediately upon closing the circuit. This means for providing a precharge to the commutatingcapacitor 15 comprises a high resistance resistor 28 having one terminal connected to the upper plate of the commutating capacitor 15 and the remaining terminal connected to the negative terminal of the direct current power supply. In addition, a second silicon controlled rectifier 29 is connected between the junction of the load 12 and one of the contacts of the separable contacts 11 for preventing premature discharge of commutating capacitor 15. This second silicon controlled rectifier 29 has its control gate element operatively connected through a current limiting resistor 24 and a blocking diode 25 to the secondary winding of a pulse transformer. Similarly, the control gate of SCR 22 is connected through a current limiting resistor 24 and blocking diode 25 to a second secondary winding 31 of the pulse transformer. The secondary windings 30 and 31 are ind-uctively coupled to the primary winding 32 of the pulse `f transformer which in turn is connected in series circuit relationship with a pulse capacitor 32a across contacts 11,

- and in parallel circuit relationship witha shunting diode As a consequence of the above arrangement, it can be appreciated that prior to placing the circuit in operation and supplying current to the load 12 through the contacts 11, that the commutating capacitor 15 will be precharged to a value determined by the value of the direct current power supply voltage and the values'of the two voltage dividing resistors 27 and 28. During the precharge of the capacitor 15, and during subsequent operation while the circuit is supplying load current to the load, the second silicon controlled rectifier 29 serves to block the potential across the capacitor 15, and prevents it from being applied to the junction of the load 12 and contacts 11. Thereafter, if it is desired to interrupt current flow to the load, the on-off switch 14 is opened to de-energize control winding 13, and cause the mechanical contacts 11 to start to separate. As in the previous embodiment of the invention, upon the mechanical contacts 11 starting to separate, an increase in potential across the contacts occurs. This results in charging pulse capacitor 32a, and produces a current pulse in the primary winding 32 of the pulse transformer which is coupled through the secondary windings 30 and 31 to the control gates of the SCRs 29 and 22, respectively. During startup of the circuit when the contacts 11 are initially closed, the shunting diode 32b causes the charging current to pulse capacitor 32a to bypass primary winding 32.

As a consequence of the above operation, both silicon controlled rectifiers22 and 29 will be rendered conductive simultaneously. Conduction of the silicon controlled rectier 29 serves to couple the upper plate of the commutating capacitor 15 effectively to one of the contacts 11, while conduction of thesilicon controlled rectifier 22 effectively couples the remaining plate of the capacitor 15 to the opposite separable contact. This results in operatively coupling the commutating capacitor 15 across the separable contacts 11 thereby preventing the formation of any substantial are discharge in the previously described manner. It is assumed that after the initial discharge of the capacitor 15 through the controlled rectifers 22 and 29, the remaining current supplied through the circuit branch including resistor 27 and SCR 22 is not sufhcient to maintain the holding current through the silicon controlled rectier 22, and it will cease conducting. Resistor 27 is designed tio have a sufficiently high value to assure this condition. From the preceding description, however, it can be appreciated that the circuit makes available an arcless interrupter circuit capable of effecting arcless in terruption, while at the same time providing a precharge to the commutating capacitor 15 so that arcless interruption is possible immediately after closure of the circuit on a load. While `one specific form of a precharge circuit has been disclosed, it would also be possible to provide a precharge to the commutating capacitor 15 with a different form of precharge circuit such as the transformer and rectifier arrangement disclosed in U.S. lPatent No. 3,042,838, Direct Current Static Electric Switch, B. D. Bedford and L. I. Goldberg, inventors, issued July 3, 1962.

A form of arcless interrupter is illustrated in FIGURE 5 of the drawings which provides along with arcless interruption, an additional feature of overcurrent protection. For this purpose, the circuit of FIGURE 5 includes an overcurrent sensing resistor 33 connected in series circuit relationship with the separable contacts 11 and the load 12. While the resistor 33 is disclosed as the overcurrerit sensing element, any form of overcurrent sensing device` could be used equally well in its place. The overcurrent sensing resistor 33 is effectively connected through limiting resistor 24, blocking diode 25 and fuse 2n to the control gate element of a second silicon controlled rectifier 35. The second silicon controlled rectifier 35 in turn is connected in series circuit relationship with a trip coil 34 for the physically separable contacts 11. The trip coil 34 acts on the contacts 11 to cause them to open in parallel with pickup and holding coil 13 which similarly can cause the contacts to be opened when it is de-energized. The series circuit formed by trip coil 34 and SCR 35 is connected across the direct current power supply so that upon the silicon controlled rectifier 35 being rendered conductive, current is supplied through the '7 trip coil 34 and results in opening the physically separable contacts 11. In other respects, the circuit of FIGURE is identical with the circuit of FIGURE 3.

vIn operation, if it is assumed that the arcless interrupter circuit of FIGURE 5 is in a current carrying condition with the contacts 11 closed and supplying current to the load 12, then in the event of an overcurrent being drawn, the potential across the overcurrent sensing resistor 33 will increase. This increase in potential will cause the second silicon controlled rectifier 35 to be tired thereby drawing current through the trip coil 34 which opens the physically separable contacts 11. As the physically separable contacts 11 start to open, an increase in potential will occur across these contacts. This increase in potential is sensed by the iirst silicon controlled rectifier 22 which is rendered conductive. As in previous circuits, upon the first silicon controlled rectier 22 being rendered conductive, the capacitor is effectively connected back across the contacts 11 so as to divert the load current therefrom, and to effect a reversal in potential across these contacts thereby avoiding the development of any substantial arc discharge across these contacts. In the selection of the value of the overcurrent sensing resistor 33, it is necessary that this resistor not be so large as to substantially increase the circuit losses during normal load carrying conditions, and it should be properly related to the value of the potential to which the commutating capacitor 15 is charged so as not to substantially decrease the value of the reverse discharge current applied back across the contacts 11 by the commutating capacitor 15 upon the SCR 22 being rendered conductive.

Still another form of direct current arciess interrupter constructed in accordance with the invention, is shown in FIGURE 6 of the drawings. The arcless interrupter shown in FIGURE 6 of the drawings is designed to effectively separate the large voltage-large current interrupter elements from the lower voltage-low current sensing circuit branches. For this reason, the arcless interrupter of FIGURE 6 is comprised by a set of physically separable contacts 11 which are connected in series circuit relationship with a load 12 across a direct current power supply. The physically separable contacts 11 are actuated by a control winding 13 which in turn is energized through an on-of switch 14. A commutating capacitor 15 is provided which has its upper plate connected to the junction of the load 12 and one of the physically separable contacts 11, and has its remaining plate operatively coupled through a gate controlled conducting device shown at il to the remaining terminal of the set of physically separable contacts 11. The gate control conducting clevice 41 in this embodiment of the invention comprises a three-electrode gap which upon the application of aV gating pulsed potential to a control electrode 42, causes the space in the gap to be ionized, allowing conduction across the gap. The gating or trigger pulse may be applied to the control electrode 42 from the midpoint of a voltage dividing or balancing network comprised by a pair of resistors 43 and 45 connected in parallel circuit relationship with ya pair of capacitors 46 and 47 respectively. If desired, the balancing network i3-47 may be omitted entirely, depending upon the three-electrode gap being used. Three-electrode gaps are well known in the art, and are commercially available through such organizations as the Power Tube Department of the General Electric Company (see Electronic Design, Ianuary 4, 1961 issue), and the Red Bank Electron Tube Division of Bendix Manufacturing Company (see Engineering Data Release, Issue No. 24, File No. G-lO, November 1960, entitled Triggered Spark Gaps). For a detailed description of other suitable three-electrode gaps, reference is also made to a Geophysics Research Directorate, Report No. AFCRC-TR55r-227, entitled Lovotron-A Low Voltage Triggered Gap Switch, dated September 1955 prepared for the Air Force Cambridge Research Center,

i Bedford, Mass.;

commutating capacitor 15 and is also connected to acharging resistor 27 which serves to charge the capacitor 15 to nearly the full potential of the direct current power supply upon the contacts 11 being closed. The control electrode 42 of the three-electrode gap is connected to a sensing and control circuit which includes essentially the secondary winding 5@ of a pulse transformer whose primary 51 is connected in series circuit relationship with a pulse capacitor 52; and a second gate controlled conducting device 53 that comprises preferably a silicon controlled rectifier. The junction of the silicon controlled rectifier 53 and the capacitor 52 is connected to a voltage dividing network comprised by a pair of resistors 54 and 55 which function to limit the potential applied to the control gate of the silicon controlled rectifier 53. It should be noted that a voltage divider is disclosed as the means employed to separate the low voltage-low current sensing circuit means from the high voltage-large current interruption circuit components, other alternative arrangements could be used equally well. The control gate of the silicon controlled rectier 53 is coupled across the contacts 11 through an electronic sensing and control network comprised by a blocking diode 56, a current limiting resistor 57, and a signal coupling network comprised by a parallel connected resistor 58 and coupling capacitor 59. In this manner, the sensing and control network is eEectively coupled across the physically separable contacts 11 so as to sense the increase of potential across the same as they commence to open.

As an alternative to the above described arrangement, it is possible to substitute a different gate controlled conducting device for the three-electrode gap 41. For example, an ignitron, a thyratron or some similar device could be substituted in the place of the three-electrode gap, and a circuit arrangement employing such a device will be described with relation to FIGURE 10.

Upon the contacts 11 being closed, and current supplied to load 12, then the commutating capacitor 15 will be charged to a value approximately equal to the value of the direct current power supply potential. Thereafter upon opening on-off switch 14 so as to de-energize the control winding 13, the separable contacts 11 will be caused to open. As the contacts 11 start to open, the increase in potential across the contacts will be sensed by the control gate of silicon controlled rectier 53 so that this device is caused to conduct. Conduction of the silicon `controlled rectifier 53 causes a discharge of the capacitor 52 through the primary winding 51 of the pulse transformer whose secondary winding Sil is connected to the control electrode of the three-electrode gap 41. Application of a voltage/current pulse to the control gate of gap 41 causes the device to conduct. Conduction through the gap 41 is limited by the resistor 48 but not by a suicient amount to prevent the diversion vof the load current away from the separable contacts 11, and the application of a reverse potential across the contacts 11 in the previously described manner so as to prevent the development of any substantial arc discharge between the contacts. In

the event some small arc discharge forms prior to discharge of the capacitor 15, it will be extinguished promptly upon the discharge of the commutating capacitor 15, and the space .between the contacts will be deionized. It should be noted that in the embodiment of the invention shown in FIGURE 6, the heavy currents to be interrupted, for example 20 amperes at 600 volts D.C., are carried by the three-electrode gap 21. These larger current carrying devices are triggered from the pulse transformer 50,

51 which in turn is actuated by the silicon controlled rectifier 53 whose low voltage-low current sensitive control gate element senses the increase in potential across the separable contacts 11. In this embodiment of the invention then the silicon controlled rectier 53 serves more as a sensing and control element to gate-n the larger current carrying and higher voltage device 41, and nee-d not be designed to withstand such larger rated voltages. In this manner, arcless circuit interruption can be extended into circuits having extremely large current and voltage ratings and still achieve arcless interruption, even though the ratings of the circuits themselves are much larger than the rating of the silicon controlled rectifier to be empolyed in the circuit for sensing opening of the contacts 11.

A diterent form of direct current arcless interrupter which is designed for effectively separatingy the high voltage-large interruption currents from the low voltage-low current sensing circuit elements, is illustrated in FIGURE 10 ot the drawings. In the circuit arrangement of FIG- URE 10, a large number of electric batteries 201 are connected in series circuit `relationship to provide a high voltage in the order of 100G-1300 volts. Current from this high voltage source is supplied to a suitable load device 202 through a current interrupter 11 connected in series circuit relationship with the load across the high voltage source 201. The load device 202 is inductive in character so that in order to optimize its decay characteristics, a thyrite resistor 203 is connected across it. The thyrite resistor 203 is connected in series circuit relationship with a pair of voltage dividing resistors 204 and 205 and parallel connected diodes 206 which serve to decouple the voltage dividing resistors 204 and 205 from the arrangement during current decay through the load 202. During normal operation of the load 202, however, the high value resistances 204 and 205 are connected in series with the thyrite resistor 203 across the load so as to yrepresent essentially an infinite impedance thereby effectively decoupling the thyrite resistor 203 from the circuit.

Arcless interruption is provided through the set of physically separable contacts 11 by means of a commutating capacitor 15 which has its upper plate connected to the junction of the load 202 and one of the contacts 11,' and the lower plate connected through an adjustable discharge current limiting resistor 207 and gate cont-rolled conducting device 208 to the remaining contact 11. The commutating capacitor 15 also has its lower plate connected through a charging resistor 211 and 'through a set of normally open lcontacts 212 to the positive terminal of the direct current power supply. During normal conduction intervals of the circuit, the contacts 212 will be closed so that the capacitor 15 can be charged essentially to the potential of the direct current power supply 201. In `order to assure discharge of the capacitor 15 when the circuit is not in operation, a discharge resistor 213 is connected in series circuit relationship with a normally closed contact 214 across the commutating capacitor 15.

The fast acting gate controlled conducting device 208 comprises an ignitron whose control gate is connected to the secondary winding 215 of a pulse transformer that comprises part of an electronic sensing and control circuit means. The pulse transformer has its primary winding 215 connected in series circuit relationship with a pulse capacitor 217 across a second fast acting gate controlled discharge device 218 that preferably comprises a silicon controlled rectiiier. For pulse shaping purposes, a pair of series connected diodes 210 are connected in parallel across the primary winding 216 of the pulsetransformer. In order to provide protection for the silicon controlled rectifier 218, a balancing network comprised by a pair of series connected resistors 219 and 220 is connected in parallel with the SCR 218 and a blocking diode 221 which is connected in series circuit relationship with the SCR. The midtap point of the two balancing resistors 219 and 220 is connected directly to the junction of the blocking Vacross the contacts 11.

diode 221 and SCR 218 in order to clamp the potential at this junction to the normal potential of the midtap point of the voltage dividing resistors 219 and 220. To further protect the silicon controlled rectier 218, a small saturable reactor 222 is connected between the pulse capacitor 217 and SCR 218 in order to hold olf the major portion of the discharge of the capacitor 217 for a predetermined period after the SCR 218 is turned on to allow time for charges to be spread throughout the semiconducting layer of the SCR. This hold-off period may amount to several microseconds, but is not sutiicient to detrimentally affect the fast-acting nature of the circuit.

The control gate of the SCR 218 is connected through a current limiting fuse 223 and two series connected blocking diodes 224 to a voltage dividing network comprised by a Zenerdiode 225 and a series connected resistor 226 and capacitor 227. The Zener diode 225 serves to clamp the maximum value of the potential applied to the control gate of the SCR 218 to a predetermined potential value above the potential of the negative terminal of the direct current power supply. '.In order to protect the Zener diode 225 it is directly connected to the intermediate point of a voltage divider comprised by a resistor 228 connected in series circuit relationship with la second resistor 229 By this arrangement, any rise in potential appearing across the set of movable contacts 11 will be transmitted through the coupling capacitor 227, resistor 226 and blocking diodes 224 to the control gate of the silicon` controlled rectier 218, and results in turning on the SCR. Upon this occurrence, a current pulse will be -discharged from the pulse capacitor 217 (after a substantial portion of the current has been held off for the predetermined period by the small saturable reactor 222) through the primary winding 216 of the pulse transformer. This results in the production of a sharp gating pulse in the secondary winding 215 which turns on ignitron 208.

In order to properly protect the interrupter circuit while placing it in :operation and in taking it out -of operation, a number of protective switches and overload trips are included in the circuit of FIGURE 10. These switches include an overload trip coil 231 connected kin series circuit with a normally open contact 232 and associated blow out coil 233 to the negative terminal ofy the direct current power supply 201. The juncture of the small saturable reactor 222 'and the Iblocking diode 221 is connected through a current limiting resistor 234, two series blocking diodesr 235, and two normally `open switch contacts 236 and 237 to .an intermediate pointon the direct current power supply 201. This intermediate point may be in a value of approximately 1A to 1/s of the total value of the potential of the direct current power supply such as 250-300 volts,- and serves to energize the sensing and control circuit means which includes the second silicon controlled rectifier 218, the pulse capacitor 217, and the pulse trans-former 215 and 216 for supply-V ing pulsed gating signals -to the ignitron 208.

To complete the protective circuitry, a master on-oft switch 238 is `connected in series circuit relationship with a lpickup and holding coil 239 across -a second portion of the direct current power supply that may be in order that from -140 volts applied a'cross the pickup an-d holding coil 239 for yoperating the arcless interrupter. Connected in parallel with the pickup and holding coil 239 is a series circuit arrangement comprised by a push Ibutton normally closed off switch 241 connected in series circuit relationship with a push button normally open Von switch 242 paralleled by a set of holding contacts 243. This arrangement is then connected in series with a second pickup and holding coil 244 through a set of normally closed overload trip contacts 245.

Upon placing the circuit arrangement of FIGURE 10 in operation, the normally open, push button on switch 242 is closed so that the yhol-ding coil 244 is energized. Energization ofthe holding coil 244 results in closing the holding contacts 243 and the normally open switch contacts 237 and 232 (with its associated blow out coil), and to open the norma-lly closed switch contacts 214 to thereby condition the arcless interrupter for operation. Thereafter, the master on-off switch 238 is closed so that the holding coil 239 is energized, and results in closing the main load current carrying intermpter contacts 11, and the contacts 236 and 212. This results in applying potential to the electronic sensing and control circuit rneans so that the charging capacitor 217 is charged essentially to the potential appearing between the tow contacts 232 and 237, namely about Z50-300 volts in the ycircuit arrangement in question. Concurrently, the commutating capacitor will `be charged through the now closed contacts 212 and charging resistor 211 to approxi-mately the full potential of the direct current power supply 201.

During operation of the arcless interrupter, the |overload current coil 231 will protect the circuit from overload current. In the event of an overload current, coil 231 will cause the normally closed contact 245 to open.

Opening of the normally closed contact 245 results in deenergizing the holding coil 244, thereby opening contacts 232 and 237. It should be noted that the holding coil 244 could also be de-energized by manual operation of the normal-ly closed push button oit switch 241. irrespective of the manner in w-hich the holding coil 244 is de-energized, it can be appreciated that upon this occurrence, the load main protective contacts 232 will open.

During normal operation of the arcless interrupter, the master on-off switch 23S will be opened to inter-rupt current iiow to the load. Opening of the switch 238 results in de-energizing coil 239 which then allows the main load current carrying contacts 11, and the contacts 212 and 236 to open. incre-ase in potential will occur across these contacts which is sensed by the electronic sensing and control circuit means and the silicon controlled rectier 218 is rendered conductive. Thereafter the current from the pulse capacitor 217, after being substantially held off for a short interval (7 microseconds) by the small saturable reactor 222, is discharged through the lprimary winding 216 of the pulse transformer. This results in producing a current gating pulse in the secondary winding 215 lof the pulse transformer which turns on ignitron 208. Upon ignitron 208 being rendered conductive, commutating capacitor 15 is allowed to discharge current back across the contacts 11 so as to effectively reduce the load current through the contacts toward zero, or, depending upon the setting of the discharge current limiting resistor 207, 4may even provide a reverse current ow across the contacts so as to effectively de-ionize the space between the contacts, thereby resulting in arcless interruption of the load current. It ,shouldy be noted that as the load current ydecays across the inductive load 2412, the blocking diodes 2116 will ihe rendered conductive so as to effectively connect thyrite resistor 263 -across the load to assist in dissipating the reactive energy stored in the load. From a consideration of the circuit arrangement in FIGURE 10, it can-|be appreciated also that the circuit does effectively isolate the low voltage-low current electronic sensing and control circuit means from the larger interruption currents and high voltages required in interrupting load current flow to the load 2112. This isolation is made possible by the use of the pulse transformer 215, 216 which provides coupling between the low voltage sensing and control circuitry and the high voltage-large current interruption circuit elements, and also allows for effective isolation of the two circuit branches.

An arcless interruptor circuit suitable for use in interrupting alternating currents is illustrated in FIGURE 7 of the drawings. In the circuit of FIGURE 7, a set of physically separable contacts 11 is connected in series circuit relationship with a load resistor 12 across the As the contacts 11 start to open, an

terminals of an alternating current supply. In the specific embodiment of the invention being considered, a 600 volt, 20 amp., 60 cycle per second alternating current source was used. A rst commutating capacitor 66 has one of its plates connected to the junction Iof the load resistor 12 and one of the separable contacts 11, and the'remaining plate connected through a ydischarge current limiting resistor 67 to a gate controlled conducting device. The gate controlled conducting device comprises a three-electrode gap 68 having one cuter electrode connected to the resistor 67, and the remaining outer electrode connected to the one of the separable contacts 11 connected directly to one terminal of the alternating current source 65 so that upon conduction through the three-electrode gap 68, the commutating capacitor 66 is eectively coupled across the set of separable contacts 11. The control electrode of the three-electr-ode gap 68 is connected to the secondary winding 71 of a pulse trans.` former whose primary winding 72 is connected in series circuit relationship with a second gate controlle-d conducting device 73 which comprises a silicon controlled rectifier. The siiicon controlled rectifier 73 in turn is coupled ldirectly across a first pulse capacitor 75 which, upon conduction through the silicon controlled rectier 73, discharges through the primary winding '72 of the pulse transformer. The pulse capacitor 75 is charged to the full voltage of an 125 volt direct current power supply by means of a charging resistor '76 connected in series circuit relationship with the capacitor 75 across the 125 vfolt direct current power supply. The voltage appearing across the gate of the silicon controlled rectifier 73 is limited by means lof a voltage divider comprised by a resistor 77 and a Zener diode 81 connected in series circuit relationship across contacts 11. The junction of the resistor 77 and the Zener diode 81 is connected through a coupling network comprised by a parallel resistor 7S and capacitor 79 to the emitter electrode of the SCR 73, and through a Iblocking diode 81 to the negative terminal of the direct current power supply. All of this -circuitry effectively serves to sense the increase in potential occurring across the set of separable contacts 11 when the alternating current supplied acrossthe terminals 65 has one polarity, and to supply a trigger signal to the control gate of SCR 73. This results in turning on SCR 73 and producing a gating pulse that is supplied through the secondary winding 71 to the control electrode of the three-electrode gap 68 to cause it to conduct. Conduction across the three-electrode gap 68 operates to connect the commutating capacitor 66 across the separable contacts 11 so as to effectively prevent the .formation of la large arc discharge across the contacts as they separate. Here again, it should be noted that the large interruption currents passing through contacts 11 are effectively isolated from the low voltage sensing and control network.

In order that the circuit operate irrespective of polarity of the alternating current potential applied across the terminals 65, a second commutating capacitor 36 is provided which is connected through a current limiting resistor `87 and third gate controlled conducting device 83 across the set of separable contacts 11. Again the gate controlled conducting device comprises a threeelectrode gap having one outer electrode connected to the resistor 87 and the remaining outer electrode operatively connected to the one of the separable contacts 11 connected directly to one terminal of the alternating current source 65. The control electrode of the threeelectrode gap 83 is connected to the secondary winding 91 of a second pulse transformer whose primary winding 92 -is connected in series circuit relationship with a fourth gate controlled conducting device comprised by a silicon controlled rectifier 93. The silicon controlled rectifier 93 and primary winding 92 of the pulse transformer are effectively connected in series circuit relationship across a second pulse capacitor 95 which, upon conduction of the silicon controlled rectifier 93, discharges through the primary winding 92 to develop a gating pulse in the secondary winding 91. The gating pulse developed in the secondary winding 91 then causes the three-electrode gap 88 to conduct so as to effectively couple the second commutating capacitor 86 across the set of separable contacts 11.

To accomplish the above, the second pulse capacitor 95 is charged to the potential of4 the 125 volt direct current power supply through a charging resistor 96. In order that the silicon controlled rectifier 93 conduct at the proper point in the alternating'current cycle, its control gate element is connected-through a blocking diode 102 and a coupling network comprised by a parallel connected resistor 98, and capacitor 99, to an intermediate point of a voltage dividing network comprised by a resistor 103 and two series connected Zener diodes 104 and 105. By this arrangement, the resistor 103 limits the potential applied to the control gate of the silicon controlled rectifier 93, and the Zener diodes 104 and 105 serve to clamp the cathode to a limited maximum potential above the negative terminal potential of the direct current supply in the event of an overvoltage such as would occur in the event of an open circuit A.C. voltage across the contacts 11. It should be noted that while a pair of Zener diodes 104 and 105 are shown, two were used merely for convenience and could be replaced by a single Zener diode having their combined rating. Also, it should be noted that the control gate of SCR 93 is effectively coupled to the one of the set of separable contacts 11 opposite to that one to which the gate of the second silicon controlled rectifier 73 is effectively coupled. It can be appreciatedV therefore, that in the event that the circuit is to be interrupted'whenV the potential applied across the terminals 65 is positive at the point 106, the control rectifier 73 will be turned on to actually interrupt the circuit. During the yalternate half cycles when the point 107 is positive with respect to the point 106, the silicon controlled rectifier 93 will be rendered conductive to initiate opera-tion of the arcless interruption.

In order to ensure that the commutating capacitors 66 and 86 are charged to the correct potential, separate charging means are provided which comprise an input transformer 111 whose primary winding is connected to a suitable source of alternating current and whose secondary winding is connected to the junction of the two commutating capacitors 66 and 86,'and to the junction of two rectifier and resistor charging circuits 112 and 113, and 114 and 115, respectively. By this arrangement, the rectifier 112 and resistor 113 will serve to charge the commutating capacitor 66 to the proper voltage level and polarity indicated, and the rectifier 114 and resistor 115 will operate separately to charge the commutating capacitor 86 to the reverse polarity of the capacitor 66as indicated by the and minus signs, and to the proper voltage level. With the commutating capacitors 66, 86 thus charged, upon conduction of its associated gate controlled conducting device 6-3 or 88, the capacitor will be coupled effectively across the separable contacts 11 to cause the load current through the contacts to be reduced to Zero, or to be reversed with respect to the initial load current flow thereby to prevent the formation of any substantial arc discharge thereacross in the previously described manner. It should be noted that in the alternating current interrupter circuit version illustrated in FIGURE 7, again the heavy commutating currents and high voltages are carried by the three-electrode gaps 68 and 88. If desired, and such devices having larger current and voltage ratings are available, then silicon controlled rectifiers such as 68 and 88 may be substituted for the three-electrode gaps, in which event the control gate elements of these devices 68', 88 will be connected respectively to the secondary windings indicated at 71 and 91 in the manner shown. Regardless of the nature of the gate controlled conducting device used, however, it can be appreciated that these devices serve to effectively couple the commutating capacitors 66 and 86, respectively, across the physically separable contacts 11 to prevent any substantial arc formation. Again, it should be noted that lower rated gate controlled conducting devices such as the silicon controlled rectifiers 73 and 93 can be used to sense the opening of the separable contacts 11, and to cause conduction of the proper ones of the larger rated gate controlled conducting devices 68 or 88, respectively, as determined by the polarity of the applied alternating current to be interrupted.

In FIGURE 8 a low cost circuit interrupter employing the principles of the present invention is illustrated, and comprises a direct current power source connected to the terminals 131, and coupled through a cable 132 to a load device 133. A set of physically separable contacts 11 is connected between the power source at 131 and the load for interrupting current fiow to the load. The distributed capacitance and inductance of the cable 132 is indicated by a bank of capacitors 135 and interconnected inductances 136, and is used as the commutating capacitor in the arcless interrupter arrangement of FIGURE 8. This parallel bank of capacit-ors 135 is connected in circuit relationship with a gate controlled conducting device 16 connected through a current limiting resistor 137 to one of the set of separable contacts 11. The remaining one of the separable contacts 11 is connected through an electronic sensing and control circuit means 17 to the control gate element of the gate controlled conducting means 16.

Upon the circuit of FIGURE 8 being placed in operation, the distributed capacitance represented by capacitors 135 will be charged essentially to the potential above ground of the power supply 131. rThereafter, upon open- Y ing of the contacts 11, the increase in potential that occurs across these contacts as they start to open will cause the gate controlled conducting means 16 to be rendered conductive. This results in effectively coupling the distributed capacitance 135 across the set of contacts 11 to thereby prevent the formation of any substantial arc discharge thereacross by imposing a reverse current iiow through the contacts 11.

FIGURE 9 of the drawings is a schematic illustration of a complete low cost circuit interrupter employing the principles shown schematically in FIGURE 8. In the circuit arrangement of FIGURE 9, a three-phase alternating current supply is coupled to a dio'de rectifier bank indicated at 140 whose rectified output is supplied across a pair of cables 141 and 142 to a load device 143. Connected in the cable 141 is a set of separable contacts 11 which can be physically separated to interrupt the current flow through the load device 143. The supply cables 141 and 142 will each have a distributed capacitance to ground v which is illustrated as the lumped capacitors 145 and 146. The circuit embodiment shown in FIGURE 9 takes advantage of this distributed capacitance by employing it as the commutating capacitor in an arcless circuit interrupter arrangement. This arrangement further includes a gate controlled silicon'controlled rectifier 147 connected in series circuit relationship with a discharge current limiting resistor 148 in a closed series loop further comprised by the set of separable contacts 11 and the distributed capacitance 145. This can be achieved in practice by effectively connecting the silicon controlled rectifier 147 to the grounded sheath of the supply cable 141.

The control gate element of SCR 147 is connected to a sensing and control circuit means that includes the secondary winding 151 of a pulse transformer connected between the control gate of SCR 147 and ground. The secondary winding 151 is inductively coupled to the secondary winding 152 of the pulse transformer, which is connected in series circuit relationship with ay second silicon controlled rectifier 153 across a pulse capacitor 154.

The pulse capacitor 154 is adapted to be charged to a predetermined voltage level and polarity, and is discharged through the primary winding 152 of the pulse transformer upon the SCR 153 being rendered conductive by its gate. The gate of SCR 153 is connected through a blocking diode 157, a current limiting resistor S, and coupling network comprised by a parallel connected resistor 159 and capacitor 161 to an intermediate point of a voltage divider network. The voltage divider network is comprised by a Zener diode 163 connected in series circuit with a resistor 164 across the contacts 11. By this arrangement, any increase in potential across the contacts 11 will be supplied to the gate of SCR 153, while the Zener diode 163 assures that this potential will not exceed a predetermined safe level.

In operation, the circuit of FIGURE 9 functions in a manner similar to that described in relation to FIGURE 1 of the drawings, and hence need not again be described in detail. It should be noted however, that the distributed capacitance 145 of the supply cable 141 in effect operates as the commutating capacitor thereby making it possible to reduce the cost of the arcless interrupter circuit considerably.

From the foregoing description, it can be appreciated that the invention makes available several new and irnproved arcless interrupter circuits for interrupting either direct current or alternating current supplied to an electric load by means of a set of physically separable contacts without producing any substantial electric arc between the contacts.

Having described several embodiments of an arcless circuit interrupter constructed in accordance with the invention, it is believed obvious that other modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention described which are within the full intended scope of the invention as defined by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An arcless circuit interrupter including in combination a set of physically separable contacts connected in series circuit relationship with a load for interrupting current to the load, a commutating capacitor and a fast acting gate controlled conducting device operatively connected in series circuit relationship across the separable contacts, electronic sensing and control means comprised by the control gate-cathode of a gate controlled solid state semiconductor device directly connected across said contacts and to the control gate of said gate controlled conducting means for sensing a potential drop across the contacts as they start to open and for rendering said fast acting gate controlled conducting means conductive in response to the opening of the contacts, and means for charging the commutating capacitor to a voltage level and polarity such that upon discharge of the commutating capacitor when the gate controlled conducting means is rendered conductive, the capacitor discharge current circulated in the closed series loop comprised by the contacts, the commutating capacitor and the gate controlled conducting means is sufficient to reduce the load current ow through the contacts to zero or to reverse the direction of current flow through the contacts with respect to the initial load current flow to thereby prevent formation of any substantial arc across the contacts upon the opening thereof.

2. The combination set forth in claim 1 further characterized by a current limiting resistor connected in the series circuit loop comprised by the commutating capacitor, the fast acting gate controlled conducting means, and the physically separable contacts.

3. The combination set forth in claim 1 wherein the fast acting gate controlled conducting means comprises a silicon controlled rectifier and said sensing and control ifi circuit is operatively coupled to the gating electrode of the silicon controlled rectifier.

4. The combination set forth in claim 1 wherein the means for charging the commutating capacitor includes means for applying a precharge to the capacitor prior to the closing of the contacts to establish current flow through the load.

5. The combination set forth in claim 1 wherein the commutating capacitor comprises the distributed capacitance of a cable.

6. The combination set forth in claim 1 wherein said electronic sensing and control means is a low Voltage-low current means which is electrically isolated from the higher voltage-higher current circuit interruptor components.

7. An arcless circuit interrupter `includin-g in combination a set of physically separable contacts connected in circuit relationship with a'load for interrupting current to the load and a control winding for controlling actuation of the contacts for causing them to open, a cornmutating capacitor, rst fast acting gate controlled conducting means connected in series circuit relationship with the commutating capacitor and the contacts for coupling the capacitor across the contacts, electronic sensing and control means operatively coupled to the physically separable contacts and to the control gate of said first fast acting gate controlled conducting means for rendering said first gate controlled conducting means conductive in response to the opening of the contacts, overload sensing means connected in circuit relationship with said load, a second gate controlled conducting means and a control winding for the physically separable contacts connected in series circuit relationship across a source of electric potential, the control gate of said second gate controlled conducting device being operatively coupled to said overload sensing means, and means for charging the commutating capacitor to a voltage level and polarity such that upon discharge of the commutating capacitorwhen the first gate controlled conducting means is rendered conductive, is sufficient to reduce the load current flow through the contacts to zero or to reverse the direction of current ow through the contacts with respect to the initial load current flow to thereby prevent the formation of any substantial arc across the contacts upon the opening thereof.

8. An arcless circuit interrupter including `in combination a set of physically separable contacts connected in circuit relationship with a load for interrupting current to the load, a commutating capacitor having one of its plates operatively coupled to one of the physically separable contacts, a first fast actin-g gate controlled conducting device operatively connected between the remaining plate of the commutating capacitor and the remaining one of the physically separable contacts for coupling the capacitor across the contacts, electronic sensing and control means comprising a second fast acting `gate `controlled conducting device, a pulse capacitor and the primary winding of a pulse transformer connected in circuit relationship across a sounce of electric potential, the control gate of the second fast acting gate controlled conductin-g device bein-g operatively coupled across `the physically separable contacts for sensing the opening thereof and the secondary winding of the pulse transformer being operatively coupled to the control gate element of the first gate controlled conducting device conductive in response to the opening of the separable contacts, and means for charging the commutating capacitor to a suflicient voltage level and polarity such that upon the discharge of the commutating capacitor when the first gate controlled conductive device -is rendered conductive, the capacitor discharge current circulated in the closed series loop comprised by `the contacts, the commutating capacitor, and the gate controlled conducting device is su'icient to reduce the load current flow through the contacts to zero or to reverse the direction of current flow through the 17 contacts with respect to the initial load current flow to thereby prevent formation of any substantial arc across the contacts upon the opening thereof. 9. The combination set forth in claim 8 further chara-cterized by a current limiting resistor connected in the series circuit loop comprised by the cornmutating capacitor, the fast acting gate controlled conductive device,

and the physically-separable contacts.

10. The combination set forth lin claim 8 wherein the first gate controlled conducting device is a three-electrode gap having -its control electrode operatively coupled to the secondary winding of rthe pulse transformer and the second gate controlled conducting device is a silicon controlled rectifier having its control gate operatively coupled across the physically separable contacts.

11. The combination set forth in claim 8 wherein the first gate controlled conducting device is a gate controlled ignitron having its control gate operatively coupled to the secondary winding of the pulse transformer, and the second gate controlled conducting device is a silicon controlled rectifier having its control gate operatively `coupled across the separable contact. I

12. The combination set forth in claim 8 wherein the first and second gate controlled conducting devi-ces comprise silicon controlled rectifiers and wherein the sensing and control means are operatively coupled to the control gates thereof.

13. 'I'he combination set forth in claim 8 wherein the cornmutating capacitor comprises the distributed capacitan-ce of a cable.

14. An arcless circuit interrupter for alternating current including in combination a set of physically separable contacts connected in series circuit relationship with a load for interrupting current to the load, a firstcommutating capacitor having one plate operatively connected to one of the contacts, first fast acting gate controlled conducting means operatively connected to the remaining contact for coupling the first cornmutating capacitor across the contacts, first electronic sensing and control means operatively coupled to one of said contacts and to .the control gate of said gate controlled conducting means for rendering said conducting means conductive in responseA to the opening of the contacts on -a given polarity of the applied alternating current, a second commutating capacitor having one plate operatively connected t-o one of the separable contacts, second fast acting gate controlled conducting means operatively connected between the remaining plate of the capacitor and the remaining contact for coupling the second commutating capacitor across the physically separable contacts, second electronic sensing and control means operatively coupled to the `remaining one of the contacts not connected to the rst electronic sensing and control means, and to the control gate of the second fast acting gate controlled conducting means for rendering the second gate controlled conducting means conductive in response to the opening of the contacts on the opposite polarity of the applied alternating current, and means for charging the cornmutating capacitors to opposite polarities and to sufficient voltage levels so that upon the fast acting gate controlled conducting devicey connected thereto being rendered conductive, the capacitor discharge current back across the contacts is sufiicient to reduce the load current liow through the contacts to zero or reverse the direction of current flow through the contacts with respect to the initial load current flow to thereby prevent any substantial arc from forming across the separable contacts as they open.

15. An arcless circuit interrupter for alternating current including in combination a set of physically separable contacts connected in series circuit relationship with a load for interrupting current to the load, -a first cornmutating capacitor having one plate operatively connected to one of the contacts, a first fast acting gate controlled conducting device operatively connected between the remaining plate of the capacitor and the remaining contact for coupling the first capacitor across the contacts, first electronic sensing and control means comprising a second fast acting gate controlled conducting device, a first pulse capacitor .and the primary winding of a first pulse transformer connected in circuit relationship across a source of electric potential, .the control gate of the second gate controlled conducting device being operatively connected to one of the separable contacts for rendering said second conducting means conductive in response to the opening of the contacts, and the secondary winding of the pulse transformerv being operatively coupled to the control gate element of the first gate controlled conducting device for rendering the rst gate controlled device conductive in response to the opening of the -separable contacts, a second cornmutating capacitor having one plate operatively connected to one of the separable contacts, a third fast acting gat-e controlled conducting device operatively connected between the remaining plate of the second cornmutating capacitor and the remaining separable contact for coupling the second cornmutating capacitor across the separable contacts, second electronic sensing and control means comprising a fourth fast acting gate controlled conducting device, a second pulse capacitor and theprirnary winding of =a second pulse transformer connected incircuit relationship across a source of electric potential, the control gate of the fourth gate controlled conducting device being operatively connected to the one of the separable contacts not connected to the second gate controlled device for rendering the fourth gate controlled 4device conductive in response to the opening of the contacts with a Igiven polarity of the applied alternating current, and the secondary winding of the second pulse transformer being operatively coupled to the control gate element of the third fast acting gate controlled conducting device for rendering the third gate controlled device conductive in response to the opening of the separable contacts on a given polarity of the applied alternating current, and means for charging the cornmutating capacitors to opposite polarities and to sufficient voltage levels so that upon the fast acting gate controlled conducting device connected thereto being rendered conductive, the capacitor discharge current back across the contacts is sufficient to reduce the load current flow through the contacts to zero or reverse the direction of current flow through the conta-cts with respect to the initial load current flow to thereby prevent any substantial arc from forming across the separable contacts as they lopen.

16. The combination set forth in claim 14 wherein the first :and third gate controlled conducting devices comprise `three-electrode gaps having the control electrodes thereof operatively coupled to the sec-ondary windings of the pulse transformers, and wherein the second and fourth gate controlled devices comprises silicon controlled rectifiers having their control gates operatively coupled to the separable contacts.

17. An arcless circuit interrupter including in combination a set of physically separable contacts connected in series circuit relationship with a load for interrupting current to the load, a commutating capacitor, fast acting gate controlled conducting means operatively connected in series circuit relationship with the commutating capacitor and the physically separable contacts for coupling the cornmutating capacitor across the contacts, electronic sensing and control means including the control gate cathode circuit of a silicon controlled rectifier directly connected across the contacts for sensing the increase in potential as the contacts start to separate and for rendering said conducting means conductive in response to the opening of th-e contacts, and means for charging the capacitor to a sufficient voltage level and polarity so that upon its discharge when the gate controlled conducting device is rendered conductive, the capacitor discharge current circulated in the closed series loop comprised by the physically separable c-ontacts, the commutating capacitor and the fast :acting gate controlled conducting means, is sufficient to reduce the load current ow through the contacts to zero or to reverse the direction of current ilovv through the contacts with respect to the initial load curpacitance of a cable.

19. The combination set forth in claim 17 further characterized by a current limiting resistor connected in the closed series circuit loop comprised by the commutating capacitor, the fast acting gate controlled conducting means, ,and the physically separable contacts.

20. An arcless circuit interrupter for alternating current including in combination a set of physically separable contacts connected in `series circuit relationship with a load for interrupting current to the load, a fir-st commutating capacitor, first fast acting gate controlled conducting means operatively connected in series circuit relationship with the capacitor and the separable contacts for coupling the first capacitor Iacross the contacts, first electronic sensing and control means including the control gate of `a silicon controlled rectifier operatively coupled to the contacts for sensing the increase in potential as the contacts start to separate and for rendering said fast acting gate controlled conducting means conductive in response to the opening of the contacts on a given polarity of the applied alternating current, a second commutating capacitor, second fast acting gate controlled conducting means operatively connected in series circuit relationship with the second capacitor and the separable contacts, secon-d electronic sensing `and control means including the control gate of a silicon controlled rectifier operatively coupled to the contacts for sensing the increase in potential across the contacts as they start to open, and for rendering the second gate controlled conducting means conductive in response to the opening of the contacts on the opposite polarity of the applied alternating current, and means for -charging `the commutatingcapacitors to opposite polarities and to a sufiicient energy level so that upon the gate controlled conducting device connected thereto being rendered conductive, the capacitor discharge current back across the contacts is sucient to reduce the load current flow through the contacts to zero or reverse the direction of current flow through the contacts with respect to the initial load cur- -rent flow to thereby prevent `any substantial arc from forming across the separable contacts as they open.

21. The combination set forth in claim 8 further characterized by voltage limiting means operatively coupled to the control gate of the second fast acting gate controlled. device for preventing substantially the full circuit voltage from being applied to said control gate.

References Cited by the Examiner UNITED STATES PATENTS 1,681,196 8/1928 Rudenberg et al 317-11 1,792,340 2/1931 Wellman 317-11 2,208,399 7/ 1940 Slepian 317-11 2,292,174 8/1942 Suits et al 317-11 2,789,253 4/1957 Vang 317-11 2,849,659 8/1958 Kesselring 317-11 3,158,786 10/1964 Hurtle 317-33 3,237,030 2/1966 Coburn 317-11 X 3,260,894 7/1966 Denault 317-11 MILTON O. HIRSHFIELD, Primary Examiner.

R. V. LUPO, Assistant Examiner. 

1. AN ARCLESS CIRCUIT INTERRUPTER INCLUDING IN COMBINATION A SET OF PHYSICALLY SEPARABLE CONTACTS CONNECTED IN SERIES CIRCUIT RELATIONSHIP WITH A LOAD FOR INTERRUPTING CURRENT TO THE LOAD, A COMMUTATING CAPACITOR AND A FAST ACTING GATE CONTROLLED CONDUCTING DEVICE OPERATIVELY CONNECTED IN SERIES CIRCUIT RELATIONSHIP ACROSS THE SEPARABLE CONTACTS, ELECTRONIC SENSING AND CONTROL MEANS COMPRISED BY THE CONTROL GATE-CATHODE OF A GATE CONTROLLED SOLID STATE SEMICONDUCTOR DEVICE DIRECTLY CONNECTED ACROSS SAID CONTACTS AND TO THE CONTROL GATE OF SAID GATE CONTROLLED CONDUCTING MEANS FOR SENSING A POTENTIAL DROP ACROSS THE CONTACTS AS THEY START TO OPEN AND FOR RENDERING SAID FAST ACTING GATE CONTROLLED CONDUCTING MEANS CONDUCTIVE IN RESPONSE TO THE OPENING OF THE CONTACTS, AND MEANS FOR CHARGING THE COMMUTATING CAPACITOR TO A VOLTAGE LEVEL AND POLARITY SUCH THAT UPON DISCHARGE OF THE COMMUTATING CAPACITOR WHEN THE GATE CONTROLLED CONDUCTING MEANS IS RENDERED CONDUCTIVE, THE CAPACITOR DISCHARGE CURRENT CIRCULATED IN THE CLOSED SERIES LOOP COMPRISED BY THE CONTACTS, THE COMMUTATING CAPACITOR AND THE GATE CONTROLLED CONDUCTING MEANS IS SUFFICIENT TO REDUCE THE LOAD CURRENT FLOW THROUGH THE CONTACTS TO ZERO OR TO REVERSE THE DIRECTION OF CURRENT FLOW THROUGH THE CONTACTS WITH RESPECT TO THE INITIAL LOAD CURRENT FLOW TO THEREBY PREVENT FORMATION OF ANY SUBSTANTIAL ARC ACROSS THE CONTACTS UPON THE OPENING THEREOF. 